Method for exchange data between a plurality of subscribers by means of a data bus

ABSTRACT

The invention relates to a method for exchanging data between a plurality of subscribers (K 1,  K 2,  K 3,  K) by means of a data bus. The subscribers are located in their totality in at least two spatially and physically separate subordinate data buses and exchange, in the interval in which the more rapid data bus is not busy, data via control devices that are associated with every subordinate data bus and that are interconnected via a more rapid data bus.

[0001] The invention relates to a method of exchanging data between a plurality of subscribers by means of a data bus.

[0002] In the case of modern vehicles, several, preferably standardized, data buses are increasingly used. For engine and chassis components, for example, one system is used which is adapted to this application case; for audio and telecommunication peripheries, another bus system is used which is particularly suitable for that purpose. The data exchange between the different bus systems takes place by way of several gateways.

[0003] The attempt to transfer this bus system architecture of higher-priced vehicles to vehicles of the lower classes results in high expenditures. The reasons are, on the one hand, the basically high costs of the standard bus for engine and chassis components and, on the other hand, the cost of a gateway. The construction of a separate onboard power supply structure for vehicles of the lower classes results in the problem that it is largely impossible to take over individual components of the higher-priced vehicles because of a lack of compatibility. In addition, a conflict exists with respect to targets. For lowering the cost, the transmission rate can be reduced and the number of bus subscribers can be increased. The result are long response times and a low flexibility because subscriber numbers differ from one vehicle to the next. Every addition of a new subscriber, for example, as a result of a subsequently installed component, requires considerable adaptation expenditures.

[0004] It is an object of the invention to provide a method of exchanging data between several subscribers by means of a data bus which, despite a plurality of subscribers varying also in a vehicle-specific manner, has a high efficiency.

[0005] The invention achieves this object by means of the characteristics of claim 1.

[0006] The onboard power supply structure according to the invention is modular and cost-effective. It permits the use of basic components in all vehicles covering several model series of a manufacturer. The higher-quality vehicles can be arbitrarily equipped by means of additional components without being more expensive than comparable series systems.

[0007] The prerequisite for the above is the existence of the faster data bus. This may, for example, be a data bus as described in German Patent Documents DE 19636441 A and DE 19636442 A. This data bus is distinguished by a transmission rate of more than 5 Mbits/s and is suitable, for example, for passive safety systems, which comprise air bags, belt tighteners, etc. as well as the pertaining sensor system and actuators as well as their control units.

[0008] These pertaining control units are situated at different points of the vehicle, for example, in the area of the transmission tunnel and of the B-columns, also in the door or at the steering column. All these control units are connected with the data bus which, in normal situations, thus outside a crash phase or serious misuse phase, is not very utilized. The same applies to the utilization of the processors in the control units.

[0009] According to the invention, these control units are also used for other functions. These functions are part of a different function periphery, for example, the electronic system of the vehicle body, and relate, for example, to the light control, the wiper control, the central locking system and the window lift mechanism control.

[0010] The light control and the wiper control, on the one hand, and the central locking system and the window lift mechanism control, on the other hand, are each a component of a subordinate data bus which, in each case, because of the minimized number of subscribers (in the case of the light control, for example, one control unit and 10 connected subscribers), has a sufficient response time and is operable also in the case of a small transmission rate; that is, rapidly and securely provides the connected subscribers or causes the connected subscribers to be provided with the required data. This also makes it possible to connect control units, which are a component of the electronic system of the vehicle body, with higher demands on the communication, directly to the faster data bus.

[0011] In the case of such an onboard power supply system structure, a separate data bus for the components of the electronic system of the vehicle body can be eliminated because these components are either directly or by way of control units connected anyhow connected to the faster data bus. This results mainly in an elimination of the gateway functionality and thus of separate gateways.

[0012] In the single FIGURE, the data bus structure according to the invention and an onboard power supply system of a vehicle implemented thereby are shown, and the communication process implemented thereby is described.

[0013] The block diagram illustrated in the FIGURE contains, among other things, a control unit module SGM and control units marked S1 to S4. In their entirety, these components are part of a passive safety system and are connected by a faster data bus “S1 bus” of a transmission rate of, for example, 5 Mbits/s. Control units marked “K” are connected to these control units, the control units marked “K” each separately forming a subordinate data bus K-bus cluster 1, K-bus cluster 2, K-bus cluster 3, . . . . The subordinate data buses are each coupled to the control units S1 to S4 as well as to the control unit module SGM. The components SGM and S1 to S4 therefore contain the functions of the safety system as well as the basic functions of the electronic system of the vehicle body. Within the subordinate data buses, several control units K are separately marked K1, K2 and K3 for further explanations.

[0014] With respect to the basic functions of the electronic system of the vehicle body, the control units SGM and S1 to S4 adapt the data of the subordinate data bus subscribers with respect to their format to the data format of the faster data bus or convert the data from this format to the data format of the subordinate data bus. They also control the feeding of these data of the subordinate data bus subscribers to the faster data bus or, inversely, guide the data of the subscribers of the other subordinate data buses to the subscribers of their connected subordinate data bus.

[0015] For this purpose, the data of all subordinate data bus subscribers and the subscribers of the faster data bus are provided with an unambiguous identification. The identifications of the subscribers of the connected subordinate data bus are stored in the respective control unit.

[0016] The special advantage of the data bus structure according to the invention consists of the fact that the number of telegrams per subordinate data bus is significantly lower than in the case of a data bus with only one branch and, as a result of the small number of subscribers, the waiting time to a possible bus access is short.

[0017] In order to obtain a system which is as flexible as possible, it is necessary that subordinate data bus subscribers (in the case of K-bus subscribers) basically have access to all required information of the overall system. In addition, it should be possible without any basic change to “clamp over” a K-bus subscriber from one subordinate data bus to another. As a result, it is possible, for example, to place a window lifter switch block in one vehicle series in the door and in the other vehicle series on the center console.

[0018] The K-bus addresses are unambiguous in the entire system.

[0019] The corresponding K-bus telegrams are relocated according to a fixed rule to bus telegrams of the faster data bus with corresponding IDs. In the control units SGM and S1 to S4, encodable “mini-gateway tables” then cause the relocation of only those telegrams which are needed in the respective subordinate data bus. During the “transfer” of one control unit K from one subordinate data bus to another, only these gateway tables must then be recoded. The overall system behavior therefore remains absolutely unchanged.

[0020] The data exchange within the overall system is explained by an example.

[0021] The transmission of a K-bus telegram TK1 from subscriber K1 at the K-bus cluster 1 to subscriber K2 at the K-bus cluster 2 is described as an example.

[0022] K1 sends telegram TK1 to K-bus cluster 1, triggered, for example, by a pressure on a key. SGM receives TK1 and wraps the telegram TK1 into the data field of an S1 bus telegram.

[0023] All S1 bus subscribers receive TK1 in the S1 bus format and check in their respective gateway tables whether TK1 is to be transmitted to the pertaining K-bus cluster. S1 unwraps TK1 from the S1 bus format and transmits TK1 to the K-bus cluster 2. K2 receives TK1.

[0024] If the telegrams of the K-bus subscribers have a longer telegram length than that of the data of the S1 bus, for example, 32 bytes of useful data in comparison to 12 bytes of useful data, a segmented, that is, repeated, transmission of defined telegram parts is required.

[0025] If, for any reason, not K2 but K3 is to receive the TK1, TK1 only has to be deleted from the gateway table of S1 and be entered into the gateway table of S2. 

1. Method of exchanging data between a plurality of subscribers by means of a data bus, characterized in that the subscribers, in their entirety, are arranged in at least two spatially and physically separate subordinate data buses, and in that, by way of control units assigned to each subordinate data bus and mutually connected by way of a faster data bus, they exchange date during the time in which the faster data bus is not busy.
 2. Method according to claim 1, characterized in that the control units adapt the data of the subordinate data bus subscribers with respect to their format to the data format of the faster data bus or convert them from this format to the data format of the subordinate data bus.
 3. Method according to claim 1 or 2, characterized in that the subordinate data bus subscribers and the subscribers of the faster data bus have an unambiguous identification.
 4. Method according to one of claims 1 to 3, characterized in that the identifications of the subscribers of the connected subordinate data bus are stored in the respective control unit.
 5. Method according to one of claims 1 to 4, characterized in that the identifications of the subscribers of the not connected subordinate data bus(es) are stored in the respective control unit.
 6. Method according to one of claims 1 to 5, characterized in that the identifications of the (not) connected subscribers are contained in a programmable memory.
 7. Method according to claim 6, characterized in that, by means of the memory content, the data transmission is controlled from the subordinate data bus to the faster data bus and vice-versa. 